iMac won't go into sleep mode in Yosemite

My 2009 iMac won't sleep either since updating to Yosemite. Tried everything short of wiping disk and reinstalling and I have no intention of doing that. It would surprise me if Apple would do anything to address our issues with the release of El Capitan being so close. Come on, Apple. SURPRISE ME!!!

Have you tried clearing the printer queue? It seems to be a general solution.

Yup, mayhewcl. My printer queues were empty for both printers. Even so, I deleted the printers in the system preferences and disconnected all cables, except the keyboard and restarted. Still wouldn't sleep. Restarted in safe mode, still wouldn't sleep. Permissions have been repaired, Bluetooth is off, all file sharing is off, in energy saver 'wake for network access' is off. I remember when I could answer "Because things just work" when people asked me why I use a Mac and not a PC. Now I just say "Because I'm stubborn"

Try this: In Energy Saver, select all 3 options. Worked for me anyway.

Thanks for your suggestion, Ryan. No difference though :-( Updated to El Capitan and the problem persists. However, neither the Yosemite update or El Capitan broke my Bootcamp partition like so many others have experienced. I can still boot into Windows XP. Go figure

Thank you mayhewcl

This worked for me!

 ▹ System Preferences ▹ Print & Scan ▹ Open Print Queue...

Check all printers for unfinished jobs. Deal with any you find.

Thank you so much for this comment. This solved my problem!

I have a mac mini server mid 2010, with Yosemite.

I was having this same problem with my iMac not sleeping after upgrading to yosemite. My keyboard is apparently the problem. I unplug that and the computer is able to sleep. I'm not sure how to fix this but at least the issue is identified.